Possible warnings (3)

kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
kernel/cgroup.c:2251:23: warning: 'root' may be used uninitialized in this function [-Wuninitialized]
kernel/sched/cpuacct.c:300:7: warning: format '%lld' expects argument of type 'long long int', but argument 4 has type 'clock_t' [-Wformat]